Xianahru said:
I dont recommend buying capture cards for single PC setups, they will ofload the CPU a tiny bit. Encoding hits the CPU, nothing a capture card will change about.
From experience and from anything you can find and read, this is actually not true. The entire purpose of a capture card is to utilize the hardware encoder that it comes with, meaning less strain and stress on the CPU. The primary reason second rigs are used, is because as gamers we do not wish to have ANY hit whatsoever, no added strain so the game runs at what we are comfortable playing it in. [Especially for those whom play BF3, Crysis 3, Skyrim etc at Ultra settings.]
So while it does not completely remove CPU usage, it definitely minimizes the strain put on a rig. Been streaming games on a single rig for a while now using OBS, the difference a capture card makes to your usage is easily noticeable.
As to stay on topic, it should work with OBS, a few people have discussed using it here as well. As far as not losing a single frame, it all depends. Strong PC setups obviously are required for more intense settings etc, but if you are looking for a foolproof 100% guarantee, well there is no such thing on a single rig setup. :D